Locking means for pivotal joints



Dec. 8, 1953 s. w. ALDERSON LOCKING MEANS FOR PIVOTAL JOINTS Filed April 21, 1952 'lNVE/VTOR SAMUEL W ALDERSON ATTORNEY Patented Dec. 8, 1953 UNITED STATES PATENT OFFICE 1 Claim. 1

This invention relates to prosthetic devices and particularly to muscular controlled locking means for pivotal joints in artificial limbs.

The object of the invention is to provide a. locking means for an artificial limb joint whereby the limb may be held firmly in the last position to which it has been moved after the amputee has relaxed the effort required for the control thereor". By way of example, a lock for an artificial arm turntable must be capable of sustaining a comparatively heavy load, for the amputee may encounter a situation where it is necessary to lift and hold a considerable weight for some time and while the use of the turntable is not in great demand its action must be positive yet easily controlled.

The invention consists essentially of an artificial limb section constructed of two parts, one

axially movable with respect to the other, as the shoulder portion of an upper arm section having an elbow portion axially supported thereby and rotatably movable with respect thereto. The elbow portion is provided with an arcuate rack and the shoulder portion is provided with a dog in cooperative relationship with said rack. The tooth or teeth on the end of said dog are normally in engagement with the teeth of said rack. A cable is attached to the opposite end of said dog in such a mannerthat the dog may be pulled away from the rack to free the elbow portion of the said upper arm section so that the forearm section of the artificial arm may be swung about as when the amputee wishes to raise his hand above his head. The cable may be pulled by the flexing of some muscle such as the pectoralis major or the infraspirratus. A means for translating the flexing of a muscle is disclosed in my application for patent, Serial Number 273,865 filed February 28, 1952, and such disclosure is by this reference incorporated herein and made a part hereof. Such means consists essentially of a plate or bearing surface sunk comfortably into the surface of the muscle and operating the end of a bell crank so that as the muscle is flexed the surface thereof will tend to straighten and will thereby push the said bearing surface outwardly. The bell crank and bearing surface are mounted on a comparatively large area plate which will move in accordance with the general movement of that part of the body whereby only a genuine flexing of the muscle and not an accidental movement of the muscle or a general body movement will operate the control cable. The cable is passed through a sheath so that as a whole it may be bent in any and with other parts of the prosthetic device,

A feature of the invention is an artificial limb section divided into two portions, one axially movable with respect to the other and normally latched together by a rack on one portion and a cooperating dog on the other. The two portions may be unlatched by a pull on a control cable operated by a muscular movement at any desired place on the amputees body.

Another feature of the invention is the use of a'cable extending from a bell crank on a muscular control device to a bell crank mounted on one portion of an artificial limb to translate an outward muscular thrust into a lifting movement of the said dog to disengage it from the arcuate rack to allow free movement of the lower or forearm section of an artificial arm.

Other features will appear hereinafter.

The drawings consist of one sheet having four figures, as follows:

Fig. l is a vertical section of part of an upper arm section of an artificial arm;

Fig. 2 is a sectional view looking downwardly from the plane including line 2--2 Fig. 3 is a similar View looking downwardly from the plane including line 3-3; and

Fig. 4 is a perspective view showing how the prosthetic device is suspended from a shoulder cap worn by an amputee.

The device of the present invention shown in one of its applications consists of a turntable control placed in an upper arm section of an artificial arm. In general the amputee is provided with a shoulder cap I, constructed of a stiff plastic casing, custom fitted to the amputees shoulder. This cap is sufficiently still to support pivots 2 and 3 whereby a yoke t is hung from the shoulder cap to support the art'mcial arm in a manner through which the arm as a whole may be abducted. The yoke t, actually shown as two pieces '5 and 5, supports the upper portion 6 of an upper arm section. An axle 8, is journalled in the body of a lower portion 1 of the said upper arm section. Bearings 9 and lil facilitate the axial movement of the portion 1. The said lower portion terminates in means for rotatably supporting a forearm section I l, as indicated in Fig, 4.

An arcuate rack 12 is affixed to the body of the portion '1, having teeth provided for the greatest expected extent of movement of the arm. A cylinder 13 is secured to the upper portion 8, containing a spring It bearing against a ring i5 fixed to the dog [6 to normally force the dog I6 downwardly. The dog it is fitted with a cap ll having teeth on its lower surface which will cooperate with the. teeth of the rack l2. Thus,

in normal position, the lower portion 1 will be effectively latched to the upper portion 6.

To operate the device, the amputee executes a muscular movement, whereby the cable 18 is pulled toward the right (Fig. 1) so that a bell crank l9, pivoted at 20 to the upper portion 6 is rotated in a clockwise direction to lift the dog IS. The cable 58 is enclosed in a sheath 2!, long enough to allow any expected movement of the arm'and to be properly hidden under the amputees clothing.

A means for moving or abducting the arm is shown in Fig. 4 as a cable 22, moving through sheaths 23 and 24. A strain on this cable 22 will raise the arm. If the elbow-i's-lo'ckedfthe arm as a whole will be moved outwardly 'fromthe body. If the elbow is freed, then'the forearm is first abducted and then the arm as a whole-is raised. If the turntablelock is freed by a strain on the cable (8, the forearm may be swung outwardly so that the amputee may raise his hand above his head.

The muscular control means is indicatedby the part 25 which forms an anchor for the end of the sheath 2i. {he control device, while a cooperating element of the present invention, is conventional and therefore not shown-in detail.

What is claimed is:

In a prosthetic device, a shoulder cap having a surface overlaying the pectoral muscle, an articulated arm pivoted thereto, arm including an upper arm section divided into two ele ments joined by a swivel joint whereby the lower of said elements "may be rotated about the longi-' tudinal axis of said arm, a lock for securing said elements against relative movement consisting of 4 an arcuate rack fixed to the lower of said elements and a cooperating latch mounted on the upper of said elements, said latch comprising a longitudinally movable pin having teeth on one end thereof mounted in cooperative relationship with the teeth of said rack, a casing for guiding said pin, a spring for normally forcing said pin into engagement with said rack, a bell crank pivotedon saiol upper element of said upper arm section having one arm thereof pivoted to said latch pin, a cable sheath anchored at one end t'osaid upper element and at the other end to said cap at the iocation'of the pectoral muscle, said sheath depending in a loose loop between said anchored ends whereby said arm may be moved through a Wide range simulating all natural movements of an arm, a muscular control device secured to said shouldercap and including said cable sheath anchorage and a cable threaded through 'said'sheath fixed at one end to the other arm of said bell crank and at the other end thereof to said muscular control device.

SAMUEL WEIR LLDEIi-SON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,537,338 Fishbein et al Jan. 9, 1951 FOREIGN PATENTS Number Country Date 113,207 Great Britain Feb. 14, 1913 114,654 Great Britain Apr. 10, 1913 618,904 Great Britain Mar. 1, 1549 

